A number of neurological and other diseases are associated with the formation of protein aggregates called amyloid fibrils. Although the protein component of amyloid is different for different diseases, the three-dimensional shape of the amyloid seems to be the same in all cases. It has proven exceedingly difficult to get detailed structural information on amyloid, compromising our efforts to understand and devise treatments for Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, and an array of other devastating conditions. We have developed antibody molecules that have the unique ability to bind to amyloid fibrils, regardless of the amino acid sequence of the constituent protein. Here we propose to develop these conformational antibodies as tools to improve our understanding of the amyloid structure and how it develops in human diseases. The specific aims are to (1) develop additional antibodies and antibody fragments, (2) structurally characterize these antibodies as a novel window onto the structure of amyloid fibrils, (3) characterize the fundamental basis of the antibody-amyloid interaction, and (4) develop the antibodies into tests for detecting amyloid in tissue and serum, as well as to monitor the emergence of the amyloid motif during in vitro amyloidogenesis. The tools involved in this work will include hybridoma and phage display technology, recombinant expression, mutagenesis, protein modeling and crystallography, immunochemical binding assays, and in vitro amyloid fibril assembly reactions. Since recently described vaccine approaches to amyloid diseases such as AD depend on the generation of antibodies, characterizing the structural basis of the anti-amyloid reaction is important. It is also important to understand the structure of amyloid and how these fibrils grow, as a means toward developing agents that will compromise fibril cytotoxicity and fibril growth. Finally, as a ubiquitous alternative folding pattern of protein polymers, amyloid and its structure is of fundamental importance to our understanding of the molecular basis of life.